Helical gear pump with backed-up nonrigid casing



Oct. 12, 1954 G. H. ZIMMER, JR

HELICAL GEAR PUMP WITH BACKED-UP NONRIGID CASING 2 she'ets-sheet- 41Filed Oct. 19, 1950 Gttornegs.

Oct. 1954 G' H HLICAL GEAR PUMP WITH BACKED-UP NONRIGID CASIN FiledOct.. 19,' 1950 ZIMMER, JR 2,691,347

2 Sheets-Sheet 2 Patented Oct. 12, 1954 HELICAL GEAR PUMP WITH BACKED-UPNONRIGID CASING George H. Zimmer, Jr., S

to Robbins & Meyers,

corporation of IOhio pringfeld, Ohio, assignor Inc., Springeld, Ohio, a

Application October 19, 1950, Serial No. 191,015

(Cl. S-25) 8 Claims. l

This invention relates to a helical gear pump with a backed-up non-rigidcasing.

In a co-pending application in the names of Frederick Cameron Byram andGeorge I-I. Zimmer, Jr., Serial No. 159,079, filed April 29, 1950, nowPatent No. 2,612,845, there is disclosed a helical gear pump withY anon-rigid casing. The pump disclosed therein is very useful for manypurposes but is not entirely satisfactory in pumping against pressurefor the reason that the nonrigid casing tends to bulge outwardly andinterfere with the operation of the pump.

It is an object of the present invention to retain the advantages of thepump disclosed in said copending case in situations where the pump isrequired to pump against pressure. It is another object of the presentinvention to provide a pump similar to that disclosed in said copendingcase but wherein said non-rigid casing becomes rigid under back pressureand wherein the stator element proper is still resiliently connected tothe non-rigid casing member.

It is yet another object of the invention to provide a pump as outlinedcombined in a single unit With a driving motor therefor and to provide acasing structure such that condensation on the pump casing wallsresulting from contact of the air with the casing walls which are beingcooled by the water being pumped cannot injure the bearing of the shaftor the winding of the motor. It is yet another object of the inventionto provide modification in the arrangement of fittings for improvedperformance.

These and other objects of the invention which I shall set forth in moredetail hereinafter or which will be apparent to one skilled in this artupon reading these specifications I accomplish by that certainconstruction and arrangement of parts of which I shall now describecertain exemplary embodiments,

Reference is made to the drawings forming a part hereof and in which:

Figure 1 is a plan View of one form of pump according to the invention.

Figure 2 is a cross sectional view of the same taken on the line 2-2 ofFigure 1.

Figure 3 is an enlarged fragmentary cross sectional view taken on theline 3--3 of Figure 2.

Figure 4 is a plan view of another modification.

Figure 5 is a cross sectional view of the same taken on the line 5 5 ofFigure 4, and

Figure 6 is a fragmentary cross sectional view similar to Figure 2showing a modification in the stator member.

Briey, in the practice of my invention I usea l member 24.

pump unit in which the pump casing head is separated from the motor headproviding a ventilated space therebetween so that condensate of moistureon the pump casing wall can flow down and out of the casing withoutdamaging the bearing of the motor windings.

Referring now in more detail to the drawings and referring first to thatembodiment disclosed in Figures 1 to 3 inclusive, there is shown a motorpump unit comprising a motor enclosed within a housing indicatedgenerally at I0 and a pump` enclosed within a housing indicatedgenerally at- I I. The motor and pump housing is made in .two

portions which are secured together. by the bolts` I2. The motor properdoes not form a feature of the present invention and will therefore notbe described in detail. The motor housing I0 has a spider-like wall IIahaving perforations I2a for ventilation purposes. Centrally thereof isprovided a boss I3 within which there is mounted a ball bearing I4 forthe motor shaft I5. p

Toward the left from the spider I lar is a ventilation space indicatedgenerally at I6 and the motor casing is closed at the pump end by a headIl having a more or less frusto conical central portion I8 which isprovided with a central boss I9 and a boss 2n which is cored out toprovide an exhaust port 2 I. The boss IS is provided with a shaftaperture 22 and a recess 23 for a seal The seal member itself forms nopart of the present invention and will not be described in detail.

The pump casing II is provided with the annular flange 25 which isbolted to the head I'I by the bolts I2 and is provided with an intakeport 26.

The pump rotor indicated at 2'I is secured to the motor shaft I5 androtates on its true axis. The pump stator member comprises a cylindricalportion 28 having internal helical threads to engage with the externalhelical threads on the rotor 21. As is well known in pumpsof this .3type, the stator member has one thread more than the rotor member sothat in operation with the rotor member rotating on its true aXis thestator portion 28 will be forced to move in a cylindrical path.

The stator member is provided with a nonrigid casing portion 29 which issimilar to the funnel-shaped non-rigid casing member disclosed in saidcopending application. According to said copending application the spacebetween the portions 28 and 29 constitutes the discharge casing of thepump. As pointed out hereinabove when the pump has to operate againstpressure the portion 29 would tend to bulge and interfere with theproper operation of the pump. .According to the present inventiontherefore the portion 29 is enclosed within a rigid `casing referred tohereinabove at Il having an internal configuration conformingsubstantially to the external coniiguration of the portion 29 so thatthe portion 29 can bulge out only slightly, if at all and if it doesbulge out, it then becomes rigid against the casing portion H. Since thecasing portion 2Q becomes rigid under pressure, provision must be madeso that the portion 28 can move in a cylindrical orbit with respect tothe portion 29, and for this reason it will be observed that theinternal helical threads or the portion 28 are relieved over a distanceindicated at X from that end of the stator where the portions 28 and 29join.

I have found that a certain amount of relief is absolutely necessary inorder to permit the portion 28 to move as required with respect to theportion 29, the entire stator, including the portions 28 and 29, beingmolded from a single piece of resilient material such as rubber or thelike. I have found that the minimum length of the dimension X should bel1 per cent of the length of the portion 28. Beyond that the eiect is tocut down the working length of the pumping element and there is noreason to go beyond a 30 per cent relief. Between the members 2B and 29there is a steplike configuration indicated at 3B which I have found tobe particularly suitable. However the conguration does not need to be asshown at 3i) in Figure 2 but may be as shown at 30a in Figure 6.

Returning to the motor easing portion there are a series of cored outopenings 3i communicating with the chamber i6 so that air circulationmay take place through the openings 3|, the chamber IB, the openings vI2and the inside of the motor casing. The motor of `course gives off heatand the pump generally is ,pumping cold water. There is therefore alwaysa tendency for moisture to condense on the pump casing head. In thepresent instance the condensation would take place on the right .handside of the wall I1 and the conical portion i8 and around the boss 20.Because of the fact that ventilation is provided the degree ofcondensation is minimized and any condensation which does form simplyruns down the walls 20, i8 and i1 and can drip out through one of thecored openings 3l. Any condensation dripping onto the shaft l5 is thrownoi by means of a slinger ring 32 secured to the shaft and rotatingtherewith. In this manner condensation cannot reach the bearings hi andof course cannot have access to the motor windings.

It will also be 'observed that the `ports `2i Aand 2=6 are upwardlydirected whereas in the .said copending case the ports were laterallydirected. I have found that there is an advantage in extending the portsupwardly rather than sidewsc in that the pumping elements remainsubmerged at all times and maintain in the pump a body of liquid beingpumped to seal the pumping surfaces. This is in the nature of aself-priming or permanent priming arrangement for the pump.

It will also `be observed that a tting 33 for a line 34 leading to apressure switch 35 is provided in the upper portion of the casing asbest seen in Figure 1. In the pump shown in the Byram Patent No.2,512,764, the pressure switch `fitting was in the lower part of thecasing and had a tendency to become fouled by sediment. This objectionis avoided according to the present construction.

In Figures 4 and 5 I have shown an inexpensive pump embodying some ofthe principles of the present invention wherein the pump is separatefrom a motor. It will be observed that the rotor 21 and stator 28, 29are identical with the structure `described above, as is the casingportion Il. In this embodiment however a pump head member is provided at:l0 having an exhaust port A4| and having a shaft aperture 42 with arecess 43 for a seal 544. The casing portion H is bolted to the head 40by means of bolts 45. The entire pump casing, including the portions Iland 40 are bolted to a bearing bracket member indicated generally at 4Eby means of bolts 41. The bracket E is provided with a boss 48 having:the bearing 49 for the pump shaft 50. Since in this case the motor isseparate from the pump, there is no reason for concern as to the problemof condensation. However, the pump of Figures 4 and 5 embodies the Asameprinciples discussed heretofore in connection with the configuration andoperation of the stator member. In both the embodiment of Figures 1 to 3and the embodiment of Figures 4 and 5 the portion 29 of the stator hasan annular flange 50 which has a portion seating in an annular recess 5Iin the head portion l1 of the Figures 1 to 3 and 40 of Figures 4 and 5.The portion 29 is held in position by the ange 25 of the casing memberIl.

It will be understood that numerous modifications may be made withoutdeparting from the fundamental spirit of the invention and that Itherefore do not intend to limit myself in any manner other than thatset forth in the claims which follow.

Having now fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. A stator for a helical gear pump, comprising 'a cylindrical memberhaving internal helical grooves and a substantially cylindrical casingmember surrounding said cylindrical member and connected thereto at oneend with an annular space therebetween, said internal helical groovesbeing relieved at said end for a distance from said end to permitorbital movement of said cylindrical member with respect to saidcasing-1 member, `said stator being of resilient materia 2. A stator fora helical .gear pump, comprising a cylindrical member having internalhelical grooves and a substantially cylindrical casing membersurrounding said vcylindrical ymember and connected thereto at one endwith an annular space therebetween, said internal helical grooves beingreiieved at said end for a distance from said end which is at least 17percent of the length of said cylindrical member, said stator being ofresilient material.

3. .A stator for a helical gear pump, comprising a cylindrical memberhaving internal helical grooves and a substantially cylindrical casingmember surrounding said cylindrical member and connected thereto at oneend with an annular space therebetween, said internal helical groovesbeing relieved at said end for a distance from said end which is from 17percent to about 30 percent of the length of said cylindrical member,said stator being of resilient material.

4. A helical gear pump comprising a. stator constituted of a cylindricalmember having internal helical grooves and a substantially cylindricalcasing member surrounding said cylindrical member, connected thereto atone end with an annular space therebetween, and open at the other end,said internal helical grooves being relieved at said end for a distancefrom said end to permit orbital movement of said cylindrical member withrespect to said casing member, said stator being of resilient material,a rigid casing member having an inlet port and having an internalconiiguration conforming substantially to the external configuration ofsaid cylindrical casing member, a casing head member for closing theopen end of said cylindrical casing member and rigid casing member, saidcasing head member having an exhaust port, a shaft aperture and sealingmeans, a shaft extending through'said aperture and sealing means andhaving secured thereto a rotor having external helical grooves inoperative relationship to the internal helical grooves of said stator.

5. A pump according to claim 4, in which said internal helical groovesare relieved at said end for a distance from said end which is at least17 percent of the length of said cylindrical member.

6. A pump according to claim 4, in which said internal helical groovesare relieved at said end for a distance from said end which is from 17percent to about 30 percent of the length of said cylindrical member.

7. A pump according to claim 4, in which said inlet and exhaust portsare disposed above the engaging surfaces of said rotor and stator, andare upwardly directed.

8. A pump according to claim 4, in which an automatic pressure switch isprovided, and in which a tting for connection to said pressure switch islocated in the upper' portion of said casing head member.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,463,341 Wade Mar. 1, 1949 2,512,765 Byram June 27, 19502,532,145 Byram Nov. 28, 1950 2,545,626 Moineau Mar. 20, 1951 2,603,161Lloyd July 15, 1952 2,603,162 Lloyd July 15, 1952

